1. Field of the Invention
The invention relates to a radiation-sensitive resin composition, a method for forming a resist pattern, and a compound and a polymer.
2. Discussion of the Background
In the field of microfabrication used to produce an integrated circuit element, lithographic technology that enables microfabrication with a line width of 0.10 μm or less has been desired in order to achieve a higher degree of integration. However, since a conventional lithographic process has utilized near ultraviolet rays (e.g., i-line), it is very difficult to implement microfabrication with a line width of 0.10 μm or less (sub-quarter-micrometer microfabrication). Therefore, lithographic technology that utilizes radiation having a shorter wavelength has been developed in order to enable microfabrication with a line width of 0.10 μm or less. Examples of radiation having a shorter wavelength include a bright line spectrum of a mercury lamp, far-ultraviolet rays (e.g., excimer laser light), X-rays, electron beams, and the like. Among these, KrF excimer laser light (wavelength: 248 nm) and ArF excimer laser light (wavelength: 193 nm) have attracted attention.
Since the excimer laser light has attracted attention, a number of resist film materials used for excimer laser light have been proposed. For example, a composition (hereinafter may be referred to as “chemically-amplified resist”) that includes a component having an acid-labile group and a component that generates an acid upon irradiation (hereinafter may be referred to as “exposure”) (hereinafter may be referred to as “acid-generating agent”), and utilizes a chemical amplification effect obtained by these components has been proposed.
However, in the field of microfabrication, it has been desired to form a still finer resist pattern (e.g., a fine resist pattern having a line width of about 45 nm). Therefore, as a method capable of forming a still finer resist pattern, some methods such as shortening the wavelength of the light source of the exposure device, or increasing the numerical aperture (NA) of the lens are known. However, a new expensive exposure device is required so as to shorten the wavelength of the light source. In the case of increasing the numerical aperture of the lens, since the resolution and the depth of focus have a trade-off relationship, there is a problem that a decrease in depth of focus occurs even if the resolution can be increased.
So, in recent years, liquid immersion lithography has been known as lithographic technology that can solve such a problem. Liquid immersion lithography provides an immersion exposure liquid (e.g., purified water or fluorine-containing inert fluid) between the lens and the resist film (over the resist film) during exposure. According to this liquid immersion lithography, the exposure optical space which was conventionally filled with air or an inert gas (e.g., nitrogen) is filled with an immersion exposure liquid that has a refractive index (n) higher than that of air and the like. Therefore, the same effect as that achieved when shortening the wavelength of exposure light can be achieved even if in the case of using the conventional wavelength of exposure light. That is, there is an advantage that high resolution can be obtained without decreasing depth of focus.
According to above liquid immersion lithography, a resist pattern that exhibits high resolution and an excellent depth of focus can be inexpensively formed even if the lens provided in an existing device is used. A number of resist film materials (radiation-sensitive resin compositions) used for liquid immersion lithography that utilize such as a fluorine-containing compound as a raw material in order to improve the water repellency of the resist film have been proposed (see JP-A-2008-115203, for example). It has been proposed to use a fluorine-containing compound as a raw material for a radiation-sensitive resin composition (see JP-A-2002-327013, JP-A-2002-080431 and JP-A-2002-280202, for example).